Our results indicate DFTB/ChIMES models can be accurately determined based on relatively small training data (unit cell MD calculations in this work), even for physically complex systems such as those containing surface chemistry. Further refinement of our TiH\(_2\)  model could involve inclusion of training data from additional phases and thermodynamic state points. blackA systematic expansion of our training set could be performed by first generating an approximate model, and then performing DFT calculations on selected snapshots and refitting ChIMES repulsive parameters until convergence is reached[1]}, similar to our previous force field fitting efforts[2]}. blackRegardless, our current effort yields accurate results for bulk and surface TiH\(_2\)  properties, and our model shows strong transferability to bulk \(\alpha \) -Ti and TiH\(_4\) . The small training set could yield significant advantages for computationally challenging systems such as magnetic materials and their interfaces, where DFT data is limited and difficult to generate. Overall, our DFTB/ChIMES approach can have particular impact on myriad of research areas, such as interpretation of imaging and spectroscopy experiments on bulk and interfacial systems, where there is traditionally a strong coupling with atomistic simulation approaches.
